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(#) Missing Initializer no-arg constructor

!!! ERROR: Missing Initializer no-arg constructor
   This is an error, and is also enforced at build time when
   supported by the build system. For Android this means it will
   run during release builds.

Id
:   `EnsureInitializerNoArgConstr`
Summary
:   Missing Initializer no-arg constructor
Severity
:   Fatal
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Identifier
:   androidx.startup
Feedback
:   https://issuetracker.google.com/issues/new?component=823348
Min
:   Lint 8.0 and 8.1
Compiled
:   Lint 8.0 and 8.1
Artifact
:   [androidx.startup:startup-runtime](androidx_startup_startup-runtime.md.html)
Since
:   1.0.0
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/startup/startup-runtime-lint/src/main/java/androidx/startup/lint/InitializerConstructorDetector.kt)
Tests
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/startup/startup-runtime-lint/src/test/java/androidx/startup/lint/InitializerConstructorTest.kt)
Copyright Year
:   2020

Every `Initializer` must have a no argument constructor.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
com/example/TestInitializer.kt:5:Error: Missing Initializer no-arg
constructor [EnsureInitializerNoArgConstr]
class TestInitializer(val int: Int): Initializer&lt;Unit&gt; {
^
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`com/example/TestInitializer.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package com.example

import androidx.startup.Initializer

class TestInitializer(val int: Int): Initializer<Unit> {

}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/startup/startup-runtime-lint/src/test/java/androidx/startup/lint/InitializerConstructorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `InitializerConstructorDetector.testFailureWhenZeroNoArgumentConstructorsArePresent`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=823348.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project.

```
// build.gradle.kts
implementation("androidx.startup:startup-runtime:1.2.0")

// build.gradle
implementation 'androidx.startup:startup-runtime:1.2.0'

// build.gradle.kts with version catalogs:
implementation(libs.startup.runtime)

# libs.versions.toml
[versions]
startup-runtime = "1.2.0"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
startup-runtime = {
    module = "androidx.startup:startup-runtime",
    version.ref = "startup-runtime"
}
```

1.2.0 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about androidx.startup:startup-runtime](androidx_startup_startup-runtime.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("EnsureInitializerNoArgConstr")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("EnsureInitializerNoArgConstr")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection EnsureInitializerNoArgConstr
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="EnsureInitializerNoArgConstr" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'EnsureInitializerNoArgConstr'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore EnsureInitializerNoArgConstr ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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